Prior to Windows 10, Windows was offered with 5 years full support and 5 years extended support. Microsoft wanted to change to Windows as a Service.
To increase adoption for Windows 10, Microsoft still accepts Windows 7 and Windows 8 keys to install Windows 10. Machines with Windows 8.1 have the Windows license in the DMI so no key is needed to be entered as Windows 10 can read the DMI and activate easily.
Windows 10 home and professional now have 18 month servicing. Monthly updates add features that are activated on a semiannual basis so for most cases the process is designed to keep home computers in full service. The monthly update rollup is all that is needed to be installed.
Earlier approaches to updates were problematic which is why the idea of monthly update rollups are now the safest way to deliver feature updates. Some notable updates to DirectX 12 added more support for game developers to support new generations of video cards.
Windows 10 is also hardened against ransomware, rootkits and other malicious software tools. Microsoft has expanded the security division working with corporate and government interests under contract to continue to improve security. Given there are over 1 billion Windows 10 users, security is vital.